；A colorless gas with a sharp, pungent odor.；In the production of chlorides, refining ore in the production of tin and tantalum, for the neutralization of basic systems, as laboratory reagent, hydrolyzing of starch and proteins in the preparation of various food products, pickling and cleaning of metal products, as catalyst and solvent in organic synthesis, for oil- and gas-well treatment, in removing scale from boilers and heat-exchange equipment, pharmaceutic aid (acidifier).；Stable - contact with common metals produces hydrogen which may form explosive mixtures with air. ；